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APPPLICATION NOTE
How to Check Integration part
Between DR-GPS and Host
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1. Introduction
The purpose of this note is to help customer to check integration part between DR-GPS
module and Host(=customer’s navigation system). Even Trimble provides detailed
specification of DR-GPS, customers have encountered technical problems, which was
figured out in development period or production line. Based on our experience, the root
cause of the problem could be found out at development period, which was skipped or not
clearly determined. Through this note, customer can understand how to check their system,
which DR-GPS interfaces over I/O connector.
2. Checking Items.
Item
Vantenna
Vbackup
Voltage level of Rx & Tx
Vcc
Tacho
RESET
Reverse Signal
Vgyro
Specification
+5V
2.5~3.6V
+3.3V+/-0.2V
+3.3V+/-0.2V
3.3V
3.3V
0/3.3V
5V
Comments
Refer to GPS Antenna specification
Try power-on/off test
No pull-up to 5V
4.75~5.25V
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3. Test Procedure
3.1 Vantenna
 Measure Vantenna(: Pin2 of HIP Module) through DMM(Digital Multimeter). And measure
Voltage at GPS RF connector. There could be Voltage drop at Hip module but it is less than
0.3V. The Voltage level at GPS RF Connector should meet GPS Antenna’s spec.
 If there is Voltage ripple, measured with Oscilloscope at GPS RF connector, it should
meet GPS antenna, customer will use. Please check it with your GPS Antenna supplier.
 When GPS Antenna is put over roof, the SNR level would be like below. However GPS
antenna installation inside a vehicle results into SNR degradation. If the SNR level is so low
as 30~40dB, something ( adding high-gain antenna or reducing cable length ) should be
taken.
 Take a look at SNR ripple. It should be stable. If it fluctuates, please check current to
GPS antenna.
NOTE: When many devices share the same 5V source, please consider total power
consumption in design period.
 Try power-on/off and see how stable SNR level is stable.
3.2 Vbackup
 This application is for Host with back-up bat for DR-GPS.
 Let DR-GPS connected with Back-up BAT.
 Try Power-on/off many times. And see Voltage level (:Pin4 of HIP Module ).
 It should meet DR-GPS Spec(2.5V~3.6V)
3.3 Voltage level of Rx & Tx
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 The Voltage level of Rx( to HIP Module) should not exceed +3.1~3.5V range.
 Tx ( to Host) line should not be pulled up to 5V.
3.4 Vcc
 Prime power : +3.1VDC to +3.5VDC(3.3V typ.)
 Ripple Noise : Max 100mV, peak-to-peak from 1Hz to 1MHz
 Check Vcc(:Pin 7 of HIP Module) to GND(: Pin 8 of HIP Module ) through Oscilloscope.
 Power Consumption : Max 250mW excluding GPS Antenna. Check it with Current meter.
 Power on/off to Host and see any overshoot/undershoot is applied to DR-GPS module.
 Out of prime power range is not allowed.
3.5 Tacho
 Test configuration as below.
Function
HOST
DR-GPS
Module
Generator
LV-TTL->232
converter
Scope
PC
 Make jumper wire of Tacho Signal line(#10) from 14 I/O cable and signal line of
F.G(Function Generator).
 Connector two jumper wire to Scope.
 Ajdust F.G and see how similar Tacho signal from I/O cable is to simulated Tacho signal
from F.G.
 Try power-on/off to available devices of Host and see what happen to Tacho signal.
 Execute Dr-Monitor tool and check Tacho counts over tool.
Note : Default time interval of 0x30-02 is 200ms. So F.G is set to output 10Hz, you can see
“2” as Tacho counts.
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3.6 RESET
 Check the Voltage level of Reset(:Pin 11 of HIP Module).
 It should be pulled-up to 3.3V with 4.7kohm.
3.7 Reverse Signal
 Test Configuration.
Power
HOST
DR-GPS
Module
supply
LV-TTL->232
converter
Scope
PC
 Through scope, check voltage level (12V) from PS(Power supply ).
 Through scope, check voltage level (0/3.3V) from Reverse Signal line (:Pin 12 of HIP
Module) during PS power-on/off.
 Through Dr-Monitoring tool, check Dir. Switch Val is changing from “0” to “1” or “1” to “0”.
Note : Since we do not know whether inverter is installed in Host, applying 12V is
considered as “0” or “1” to DR-GPS module.
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3.8 Vgyro
For 5V Gyro component
 To test Vgyro part, 5mV resolution device is necessary.
 I have used Labjack U12. http://www.labjack.com/labjack_u12.php?prodId=27
 Per 5V Gyro spec, more than +/-5mV ripple of 5V Vgyro is regarded as heading(Gyro)
spinning
HOST
5V Vgyro
DR-GPS
Module
Gyro Output
Gyro
GND
Labjack
PC
 More than +/-5mV ripple is not allowed.
 Check Vgyro voltage level and power off Host. After 4h later, power on. Check Vgryo
voltage level.
 Any voltage difference(+/- more than 5mV) between 4h-ago voltage and current voltage
is not allowed.
 Try power on/off all devices, connected to 5V, of Host and see whether Vgyro is
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changing.
 12Bit ADC inside DR-GPS module consumes less than 4mA. Consider this.
For 3V Gyro component( for example, EPSON VX-8100CB)
 To test Vgyro part, 5mV resolution device is necessary.
 I have used Labjack U12
 Per 3V Gyro spec, more than +/-15mV ripple of 3V Vgyro is regarded as heading(Gyro)
spinning
HOST
3V Vgyro
DR-GPS
Module
Gyro Output
Gyro
GND
Labjack
PC
 More than +/-15mV ripple is not allowed.
 Check Vgyro voltage level and power off Host. After 4h later, power on. Check Vgryo
voltage level.
 Any voltage difference(+/- more than 5mV) between 4h-ago voltage and current voltage
is not allowed.
 Try power on/off all devices, connected to 3V, of Host and see whether Vgyro is
changing.
 12Bit ADC inside DR-GPS module consumes less than 4mA. Consider this.
4. Summary
This application note would be updated later, if more info is requested by developer.
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